In the area of optics, portable instruments capable of being used "out in the field" by technicians and service people are becoming in greater demand. As of late there have been requirements for relatively precise, reliable, portable and/or hand held devices that measure and display the frequency or wavelength of an optical signal. It is believed that devices of this sort, at an affordable cost, would be highly desirable. For example, there are instances when technicians trouble-shooting need to verify the frequency of an optical signal; perforating this "out in the field" can be an onerous task without the use of a portable measurement device. Other instances occur when a technician must connect particular optical fibers together--the connections requiring knowledge of the wavelength of signals carried on one or more of the optical fibers. Once more, a portable wavelength measurement device would offer a practicable solution.